The use of lasers in corrective and cosmetic surgery procedures is well known. In these procedures light from a laser comprised in an appropriate mechanical-optical system causes a desired cosmetic or surgical change in a region of tissue by delivering to the region an amount of energy sufficient to effect the change. A common problem often encountered in these procedures is to deliver the energy to the region, hereinafter referred to as a “target”, without delivering energy to tissue surrounding the region that might damage the surrounding tissue. Many prior art medical laser systems do not solve this problem satisfactorily and often deliver substantial amounts of unwanted and unneeded energy to tissue surrounding a target that they irradiate.
For example, laser light is often used to depilate skin by cauterizing follicles of hair to be removed from the skin. Most prior art laser depilators irradiate areas of skin much larger than the area of skin occupied by a hair follicle. As a result, most of the laser energy these depilators radiate is wasted. A major portion of the laser energy is incident on hairless areas of skin and only a small portion is incident on targets (i.e. hair follicles) on the skin and used to remove hair. Since the prior art laser depilators are energy inefficient, they generally require relatively powerful lasers that illuminate skin being treated with a high energy density of laser light. This energy density when incident on hairless regions of skin can cause thermal damage to these areas.
For example, typically 20 milliJoules (mJ) of energy are required to cauterize a hair follicle and a typical hair follicle occupies an area of skin approximately 3×10−4 cm2. An energy density of about 60 J/cm2 therefore is generally required to cauterize hair follicles. Many prior art laser depilators irradiate an area of skin on the order of 1 cm2 with a pulse of laser energy lasting about a millisecond or a fraction of a millisecond to depilate an area of skin. A Laser in one of these systems must therefore provide a peak power output of about 60,000 watts.